Heat pipe and method for manufacturing the same

ABSTRACT

An exemplary heat pipe includes a hollow tube, a wick structure configured on an inner surface of the tube and a working medium formed in the tube. Two ends of the tube are sealed and the tube defining a chamber therein. The tube comprises an evaporating section and a condensing section, and the evaporating section is isolated from the condensing section. The wick structure extends from the evaporating section to the condensing section along the inner surface of the tube to form a working medium channel. A pair of through holes is defined in each of the evaporating section and the condensing section of the tube. A pair of metal pipes communicate the through holes of the evaporating section with those of the condensing section to form a pair of vapor channels. A method for manufacturing the heat pipe is also provided.

BACKGROUND

1. Technical Field

The present invention relates generally to heat pipes and methods formanufacturing heat pipes.

2. Description of Related Art

Currently, heat pipes are widely used for removing heat fromheat-generating components such as electrical devices in computers. Aheat pipe includes a sealed tube held in vacuum but also containing aworking medium therein. The working medium is employed to carry, underphase transitions between a liquid state and a vapor state, thermalenergy from an evaporator section to a condenser section of the heatpipe. Preferably a wick structure is provided inside the heat pipe,lining an inner wall of the tube, for drawing the working medium back tothe evaporator section after it is condensed at the condenser section.In a traditional heat pipe, a vapor channel is defined in a middle ofthe tube, with the wick structure surrounding the vapor channel. Thevapor flows along the vapor channel in a longitudinal direction, and theliquid working medium flows in the wick structure reversely. A shearstress is generated between the vapor and the liquid working medium whenthey are flowing, and the shear stress reduces the heat transferringperformance of the heat pipe.

Therefore, a heat pipe and a method for manufacturing the heat pipewhich are capable of overcoming the above described shortcomings aredesired.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead being placed uponclearly illustrating the principles of the present embodiments.Moreover, in the drawings, like reference numerals designatecorresponding parts throughout the several views.

FIG. 1 is a longitudinal cross-sectional view of a heat pipe inaccordance with a first embodiment of the present invention.

FIGS. 2-7 are schematic, cross-sectional views showing sequential stepsof an exemplary method for manufacturing the heat pipe of FIG. 1.

FIG. 8 is a longitudinal cross-sectional view of a heat pipe inaccordance with a second embodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIG. 1, a heat pipe 1 in accordance with a first embodimentof the present invention includes a hollow tube 10 with a wick structure11 configured on an inner surface of the hollow tube 10. Two ends of thetube 10 are sealed, so that the tube 10 defines a chamber 12 therein. Aworking medium is provided in the chamber 12. The tube 10 is symmetricalalong a central axis thereof.

The tube 10 forms a reduced section 13 at an intermediate positionthereof. The tube 10 includes an evaporating section 14 and a condensingsection 15 located adjacent to two ends of the reduced section 13,respectively. The evaporating section 14 is isolated from the condensingsection 15, and a length of the evaporating section 14 is less than thatof the condensing section 15. An inner diameter and an outer diameter ofthe evaporating section 14 are equal to those of the condensing section15, respectively. The reduced section 13 has a middle portion 131, andtwo end portions 132 located at two ends of the middle portion 131,respectively. An inner diameter and an outer diameter of the middleportion 131 are constant, and both the inner and outer diameters areless than those of the evaporating section 14. An inner diameter and anouter diameter of each end portion 132 respectively increase along adirection away from the middle portion 131, until the inner diameter andthe outer diameter of the end portion 132 are equal to those of thecorresponding evaporating section 14 or condensing section 15,respectively.

The tube 10 has a metal layer 16 formed therein, and the metal layer 16is symmetrical about the central axis of the tube 10. The metal layer 16includes a tapered portion 161 and a cylindrical portion 162 connectedto a right end of the tapered portion 161. The tapered portion 161tapers from the cylindrical portion 162 (in a direction from theevaporating section 14 to the condensing section 15) until the taperedportion 161 terminates at a closed, pointed end. In this embodiment, thetapered portion 161 of the metal layer 16 is a hollow tapered portion.The tapered portion 161 is parallel to a right one of the end portions132, and abuts the wick structure 11 of the right end portion 132. Thus,a right section of the tapered portion 161 is attached to the wickstructure 11 of the right end portion 132. In addition, the cylindricalportion 162 of the metal layer 16 is attached to the wick structure 11of the evaporating section 14. Accordingly, the chamber 12 of the tube10 is divided into two parts by the metal layer 16, with the two partscorresponding to the evaporating section 14 and the condensing section15.

The wick structure 11 extends from the evaporating section 14 to thecondensing section 15 along the inner surface of the tube 10, therebyforming a working medium channel. Two through holes 17 are defined ineach of the evaporating section 14 and the condensing section 15 of thetube 10. Two hollow metal pipes 18 are provided. One of the hollow metalpipes 18 communicates one of the through holes 17 of the evaporatingsection 14 with one of the through holes 17 of the condensing section 15at a same side of the tube 10. The other hollow metal pipe 18communicates the other through hole 17 of the evaporating section 14with the other through hole 17 of the condensing section 15 at anothersame side of the tube 10. Thereby, two vapor channels 181 are defined bythe hollow metal pipes 18.

In operation, the evaporating section 14 of the heat pipe 1 is put inthermal contact with a heat generating electronic component (not shown).The working medium in the heat pipe 1 is vaporized after receiving theheat generated by the heat generating electronic component, and thevapor exerts pressure on the metal layer 16. However, the taperedportion 161 of the metal layer 16 tapers in the direction from theevaporating section 14 to the condensing section 15 until the taperedportion 161 terminates at the closed, pointed end. Accordingly, thevapor is blocked from moving directly toward to the condensing section15, and instead flows to the condensing section 15 via the two vaporchannels 181. The vapor condenses into liquid state working mediumslowly as it flows through the two vapor channels 181, and then flowsinto the condensing section 15. Thus, the pressure in the chamber 12 atthe condensing section 15 is decreased. The liquid working medium isdrawn back to the evaporating section 14 by the wick structure 11provided on the inner surface of the tube 10.

Therefore the flow of working medium is circulatory along two closedloops that are joined at the tube 10. The flow of working medium alongeach of the loops is essentially unidirectional, and the flow of workingmedium along the tube 10 where the loops are joined is alsounidirectional. This arrangement avoids or even completely eliminatesshear stress that is liable to be generated between vapor and liquidworking medium when the vapor and liquid working medium are flowing inopposite directions along paths that are adjacent to each other. Thus,the heat transferring performance of the heat pipe 1 can be improved.

It is understood that in alternative embodiments, the evaporatingsection 14 and the condensing section 15 can be isolated from each otherby other means. That is, other heat pipes are not limited to using themetal layer 16 of the first embodiment.

Referring to FIGS. 2-7, an exemplary method for manufacturing the heatpipe 1 includes steps as described below.

Referring to FIG. 2, a tube 20 is provided, with two ends of the tube 20being open. The tube 20 is formed with a wick structure 21 on an innersurface thereof, and defines a chamber 22 therein. In this embodiment,the tube 20 is made of a highly thermal conductive material such ascopper or aluminum. A transverse cross-section of the tube 20 is acircular ring, and the tube 20 defines a central axis. The wickstructure 21 extends along a longitudinal direction of the tube 20. Thewick structure 21 is usually a porous structure selected from finegrooves, sintered powder, screen mesh, or bundles of fiber, and providesa capillary force to drive working medium in the tube 20 to flow.

Referring to FIG. 3, a cylindrical metal layer 30 is provided andlocated in the chamber 22 of the tube 20. The metal layer 30 is attachedto the wick structure 21 of the tube 20. The metal layer 30 is close tobut spaced from a right end of the tube 20. In this embodiment, a lengthof the metal layer 30 is 20-60 mm (millimeters), and the metal layer ismade of high toughness material such as copper or aluminum.

Referring to FIGS. 4 and 5, a portion of the tube 20 containing a leftportion of the metal layer 30 is pressed to obtain a reduced section 40of the tube 20 containing the pressed portion of the metal layer 30.Specifically, a compressing tool 50 is provided. The compressing tool 50may for example include a pair of opposite pressing dies. Thecompressing tool 50 is positioned corresponding to the left portion ofthe metal layer 30. The compressing tool 50 compresses the left portionof the metal layer 30 along radial directions of the tube 20 until theleft end of the left portion of the metal layer 30 is closed. Becausethe metal layer 30 is made of high toughness material, the metal layer30 attaches to the wick structure 21 of the tube 20. In this embodiment,the reduced section 40 divides the tube 20 into the evaporating section23 and the condensing section 24, with the reduced section 40intervening between the evaporating section 23 and the condensingsection 24. Thus, the evaporating section 23 is isolated from thecondensing section 24. A length of the evaporating section 23 is lessthan that of the condensing section 24.

The reduced section 40 has a middle portion 41, and two end portions 42located at two ends of the middle portion 41. An inner diameter and anouter diameter of the middle portion 41 are constant, and the inner andouter diameters of the middle portion 41 are both less than those of theevaporating section 23. An inner diameter and an outer diameter of eachend portion 42 increase along a direction away from the middle portion41, until the inner diameter and the outer diameter of the end portion42 are equal to those of the corresponding evaporating section 23 orcondensing section 15, respectively. The wick structure 21 extends fromthe evaporating section 23 to the condensing section 24 along the innersurface of the tube 20, thereby forming a working medium channel. Alength of the uncompressed cylindrical portion of the metal layer 30 inthe evaporating section 23 is 10 mm.

The tube 20 has a working medium injected into it, and is evacuated ofair and sealed. In particular, both the evaporating section 23 and thecondensing section 24 are evacuated of air.

Referring to FIG. 6, two pairs of opposite through holes 25 are formedin each of the evaporating section 23 and the condensing section 24 ofthe tube 20.

Referring to FIG. 7, two hollow metal pipes 60 are provided tocommunicate the through holes 25 of the evaporating section 23 withthose of the condensing section 24, so that two vapor channels 61 aredefined by the hollow metal pipes 60. Thus, the heat pipe 1 ismanufactured.

Referring to FIG. 8, a heat pipe in accordance with a second embodimentof the present invention is shown. There are four pairs of through holes25 defined in the tube 20. Four hollow metal pipes 60 are provided tocommunicate the through holes 25 of the evaporating section 23 withthose of the condensing section 24, so that four vapor channels 61 aredefined by the hollow metal pipes 60. It is understood that the quantityof the through holes 25 and the hollow metal pipes 60 is not limited toeight through holes 25 and four hollow metal pipes 60.

Particular embodiments are shown and described by way of illustrationand example only. The principles and the features of the presentdisclosure may be employed in various and numerous embodiments thereofwithout departing from the scope of the disclosure. The above-describedembodiments illustrate the scope of the disclosure but do not restrictthe scope of the disclosure.

What is claimed is:
 1. A heat pipe comprising a hollow tube, two ends ofthe tube being sealed and the tube defining a chamber therein; a wickstructure provided on an inner surface of the tube; and a working mediumprovided in the chamber; wherein the tube comprises an evaporatingsection and a condensing section, the evaporating section is isolatedfrom the condensing section, the wick structure extends from theevaporating section to the condensing section along the inner surface ofthe tube to form a working medium channel, a through hole is defined ineach of the evaporating section and the condensing section of the tube,and a metal pipe communicates the through hole of the evaporatingsection with the through hole of the condensing section, respectively,to form a vapor channel.
 2. The heat pipe of claim 1, further comprisinga metal layer therein, wherein the evaporating section is isolated fromthe condensing section by the metal layer, the metal layer comprises atapered portion and a cylindrical portion connected to a right end ofthe tapered portion, the tapered portion tapers from the evaporatingsection to the condensing section until the tapered portion terminatesat a closed end thereof, and the tapered portion and the cylindricalportion are attached to the wick structure of the tube.
 3. The heat pipeof claim 2, wherein the tube further comprises a reduced section betweenthe evaporating section and the condensing section, the reduced sectionis located outside the metal layer, the evaporating section and thecondensing section of the tube have a same inner diameter and a sameouter diameter which constitute an inner diameter and an outer diameterof the tube, respectively, and an inner diameter and an outer diameterof the reduced section are less than the inner diameter and the outerdiameter of the tube, respectively.
 4. The heat pipe of claim 3, whereinthe reduced section has a middle portion and two end portions located attwo ends of the middle portion, an inner diameter and an outer diameterof the middle portion are constant, the inner diameter and the outerdiameter of the middle portion are less than the inner diameter and theouter diameter of the tube, respectively, and an inner diameter and anouter diameter of each end portion increases along a direction away fromthe middle portion until the inner diameter and the outer diameter ofthe end portion are equal to the inner diameter and the outer diameterof the tube, respectively.
 5. The heat pipe of claim 1, wherein a lengthof the evaporating section is less than that of the condensing section.6. The heat pipe of claim 1, wherein the tube is made of thermallyconductive material.
 7. The heat pipe of claim 1, wherein the wickstructure is selected from the group consisting of fine grooves,sintered powder, screen mesh, and bundles of fiber.
 8. A method formanufacturing a heat pipe, the method comprising: providing a tube witha wick structure on an inner surface thereof, the tube defining achamber therein, and further defining an evaporating section and acondensing section; insolating the evaporating section from thecondensing section by blocking the chamber, the wick structure extendingfrom the evaporating section to the condensing section along the innersurface of the tube to form a working medium channel; evacuating theevaporating section and the condensing section, injecting a workingmedium into the tube, and sealing the tube; defining at least onethrough hole in each of the evaporating section and the condensingsection of the tube; and arranging at least one metal pipe tocommunicate the at least one through hole of the evaporating sectionwith the at least one through hole of the condensing section, therebydefining at least one vapor channel.
 9. The method of claim 8, whereininsolating the evaporating section from the condensing section furthercomprises: providing a metal layer in the tube between the evaporatingsection and the condensing section, the metal layer being attached tothe wick structure of the tube; pressing the tube at the metal layer toobtain a reduced section of the tube, an inner diameter and an outerdiameter of the reduced section being less than an inner diameter and anouter diameter of the tube, respectively, one portion of the metal layerin the reduced section tapering in a direction from the evaporatingsection to the condensing section until terminating at a closed end ofsaid one portion, another portion of the metal layer in the evaporatingsection remaining attached to the wick structure of the tube, theevaporating section thereby being insolated from the condensing sectionby the metal layer.
 10. The method of claim 9, wherein the reducedsection has a middle portion and two end portions located at two ends ofthe middle portion, an inner diameter and an outer diameter of themiddle portion are constant and both less than that of the tube, and aninner diameter and an outer diameter of the end portion increase along adirection away from the middle portion until the inner diameter and theouter diameter of the end portion being equal to that of the tube. 11.The method of claim 8, wherein the tube is made of thermally conductivematerials.
 12. The method as claimed in claim 8, wherein the wickstructure is selected from fine grooves, sintered powder, screen mesh,and bundles of fiber.
 13. The method of claim 8, wherein a length of theevaporating section is less than that of the condensing section.
 14. Aheat pipe comprising a hollow tube, two ends of the tube being sealedand the tube defining a chamber therein; a wick structure provided on aninner surface of the tube; and a working medium provided in the chamber;wherein the tube comprises an evaporating section and a condensingsection, the evaporating section is isolated from the condensingsection, the wick structure extends from the evaporating section to thecondensing section along the inner surface of the tube to form a workingmedium channel, two through holes are defined in each of the evaporatingsection and the condensing section of the tube, and two metal pipescommunicate the two through holes of the evaporating section with thetwo through holes of the condensing section, respectively, to form twovapor channels.
 15. The heat pipe of claim 14, further comprising ametal layer therein, wherein the evaporating section is isolated fromthe condensing section by the metal layer, the metal layer comprises atapered portion and a cylindrical portion connected to a right end ofthe tapered portion, the tapered portion tapers from the evaporatingsection to the condensing section until closed, and the tapered portionand the cylindrical portion are attached to the wick structure of thetube.
 16. The heat pipe of claim 15, wherein the tube further comprisesa reduced section between the evaporating section and the condensingsection, the reduced section is located outside the metal layer, and aninner diameter and an outer diameter of the reduced section are bothless than that of the tube respectively.
 17. The heat pipe of claim 16,wherein the reduced section has a middle portion and two end portionslocated at two ends of the middle portion, an inner diameter and anouter diameter of the middle portion are constant, and the innerdiameter and outer diameter of the middle portion both less than that ofthe tube, and an inner diameter and an outer diameter of the end portionincrease along a direction away from the middle portion, until the innerdiameter and the outer diameter of the end portion being equal to thatof the tube.
 18. The heat pipe of claim 14, wherein a length of theevaporating section is less than that of the condensing section.
 19. Theheat pipe of claim 14, wherein the tube is made of thermally conductivematerials.
 20. The heat pipe of claim 14, wherein the wick structure isselected from fine grooves, sintered powder, screen mesh, and bundles offiber.